Means for reconditioning drill bits



Aug 1943- R. E. CALHOUN 2,326,520

MEANS FOR RECONDITIONING DRILL BITS Filed April 29, 1941 RALPH E. CALHOUN INVENTOR I ATTORNEY Patented Aug. 10, 1943 pairs" sr'iss j zszdsze i MEANs FOR RECONDITEONiNG ans. airs r Ralph E. Calhoun, Metaline r n, w sh; g 7 Application April 29, 1941, Serial Ho. 390,947

V 2 Claims. (01. "is- 9s) This invention relates to improvements in a means for reconditioning drill bits.

It is well known by those who engage in the construction and maintenance of mine tunnels or in any'operation of an engineering nature employing the drilling of holes in the earth or rock for the purpose of blasting, that the reconditioning of the worn or dulled bits of the drills presents a problem that in some respects has never been satisfactorily solved.

With the advent of the detachable bit, which has largely replaced the conventional steel of former use, the need for adequate and easily operated reconditioning mechanism has grown very acute.

A drill bit, which ordinarily has from two to four teeth or wings, when it is used loses height due to the dulling or flattening of the cutting edges of the teeth. In addition, it also loses size in gauge diameter due to the undercut nature adequate clearance of the rearward passage of dust and the like from the cutting face'of the hole being drilled.

The gauge cornersof the bit are worn away and consequently the width ofjthe bit is materially reduced from its original size; In order to get the maximum number of usages from such a bit, it is necessary thatthe original gauge diameter beregained during the reconditioning operation. Otherwise, the loss of this gauge diameter will limit the use of the bit'in subsequent drilling operation to those of less demand where such reducedsize bit may be used." Due to the temper that is given the metal of. the bit in order to make it as durableas possible during drilling operations, the reconditioning of the bit by grinding is generally unsatisfactory. Of recent years the heating of the bit and their reconditioning while'in a hot malleable condition is being practiced by other methods. I

The method disclosed herein is intended to disclose a new practice of resizing the bit to a diameter which, when it is subsequently ground and regauged, will be approximately thesame as the original gauge diameter before its initia usage.

An important objector myinvention has been the provision of a novel'me thod of reconditioning dulled drill bits so that they may subsequently be regauged to a greater diameter than when dull.

Another object of my invention has -been the provision of extremely simple, easily operated,

durable shaping means'for rock drill bits.

A further object of my invention relates to the provision of tools whereby the tooth or a dulled drill bit may be fullered or swaged to a desired size without distorting the shape of the tool or otherwise destroying its usefulnessz' Still another object of the invention'has been the provision of an improved anvil means' for receiving and holding the bit during the reshaping operation, in which anvil the bit may be readily indexed to present sequentially the various .wings of cutting teeth on the face of the bit to'be reshaped. A still furtherobject relates to the provision of a bit' tooth svvaging bar having fullering wings, which bar may be associated witha vertically reciprocating'means for bringing it easof the end of a sharpened bit tooth to provide 0 means is simple of construction and. maintem ily into andout of engagementwith a' bit tooth presented to it for reshaping.

Another object of the invention is to providean improved bit sharpening mechanism; whereby the work may be quickly performed-with a minimum amount of manipulation andjresultantly extremely low costior the individual operations.

Yet, another object of the invention is to pro- J vide improved means for positioning a drill bit' forresharpening and for supporting it while. the

pressure of swaging mechanism; is being applied 'for the resharpening operations, which ance to efiect low initial and operating costs.

Other objects and advantages of the invention will be more apparent during the course of-the following description wherein I have described my novel method and illustrated 'a preferred form of the 'mechanism by which I practice my method. It will be understood that while I have shown this mechanism having specific formand operation I do not intend to limit the scope of my invention beyond the definitions of the subjoined claims V .In the drawing: 1

Figure 1 is a viewinelevation of a drill bit that has been dulled and in connection with which is shown, in a magnified portion of the drawing, the originalcontour as well as' the resharpened contourothat results from the practice of my metliod in reconditioning suchadrill bit,

and anvil mechanism of my invention showing inconnection] therewithfla drill bit as it would appear when presentedfor reconditioning, 1

reconditioning dulled Figure '2 is an assembly View of the swage bar Referring to the drawing, throughout which.

like reference characters indicate like parts, It!

designates a drill bit having a skirt I2 and a plurality of bit teeth l4, l6 and I8. The skirt I2 is drilled and threaded at 20 for attachment to the conventional drilling bar that is designed for use with the detachable bits of this nature.

, The usual water hole through, the axial center of the bit is indicated at 22.

While I have shown in my drawing and am describing a detachable drill bit it will be understood that the practice of my, method and the use" of my mechanism is not limited to such devices. In the case of conventional steel wherein the drill teeth are formed on the end ofa regular drill shank, the same may also be sharpened as is described herein.

In the magnified portion of the drawing of Figure l, I have indicated in dashed line and also labelled (1) the original contour of the bit in solid line, (2) the contour of the dulled bit, and finally in a second dashed line lying in a lower plane, (3) the resharpened contour of the bit after employing the method of my invention. Also indicated in the encircled magnified portion of the bit is'the gauge loss between the original sharpening of the bit and its dulled diameter as well the gauge diameter that is regained when the bit is gauged after the practice of my invention; 7 1 Upon a) suitable base 24 I mount the anvil base plate'26 having thereon the anvil28. The upper surface 30 of the anvil merges with the inner surface 32 of the bit saddle 34' which is curved and flared adjacent the saddle as indicated by the numeral 36. A drill bit, as I0, is positioned in the saddle so that-the flared'outer undercut portion of the drill bit wing rests on the curved portion 36 and also against the anvil face 30. i

In the case of detachable bits, a bit shank or handle 38 is inserted into the opening 30 of the bit and is used for manually handling the bit and indexing it during the shaping operation on the anvil.

Upon a vertically movable reoiprocable head :40 I mount the attaching plate 42 of the swage bar 44. Bar ,44 may be substantially rectangular in'cross-section and should be formed of durable stock for long use in shaping the drill bit teeth.

In a lower corner of the bar 44 I form a V- shaped groove 46 which has the flared fullering wings 48,48extending therefrom. The wings may be provided with teeth as 49 or under cer-,

tain circumstances, may be perfectly smooth.

The curved surfaces 48 are designed for vertical travel to contact the sloping sides of the bit teeth-on either side of the cutting edge to be formed and to force the metal downwardly and radially outward of the bit to increase the length of the material in'which is to be formed the cutting edge of the tooth. The force of the swage' bar is against the bit tooth primarily but removed mechanically with speed.

In practicing the method the bit HI isheated to'a malleable state and so that it is somewhat annealed to remove to a degree temper in the metal. While the bit is in such a malleable .state and hot-it is affixed to the bit shanl; 38

and is presented to the anvil so that the heel of a tooth or wing rests on the surface 30 in the path of the swaging bar. The swage bar is lowered producing a fullering action of the metal forming the wing and to swage it outwardly along the axis of thetooth to increase the overall diameter of the bit stock on its cutting face.

The shaping of the remaining bit teeth is per formed sequentially one tooth after another. To perform these operations the operator or tool handler merely indexes the bit, one-quarter of a turn in the case of a four-tooth bit, to present the next tooth to the fullering wings of the swage bar. When all of the teeth of the bit have been reshaped as has been described, the bit is next presented to a conventional grinding tool for smoothing the sloping faces of the bit teeth and also to a gauging grinder for accurately circumscribing the gauge diameter of the bit.

In a subsequent operation the sharpened bit is accurately heated and retempered in the usual manner preferably by the liquid quench method to the desired degree of hardness. It has been found possible to sharpen, by the use of the mechanism shown herein and the method described in this specification, asmany as six hundred bits a day, with but a single operator handling the mechanism and performing the operation.

In sharpening certain types of drill bits the metal of the drill bit is such that a smooth-faced the axis of the cutter tooth to force the metal to the outer end thereof It is an important result of this invention, as

' it will be noted from the foregoing specification,

that my machine is especially designed for the forming of the cutting surfacesof the rock drill bit at extremely high speed in an operation that can be efiicient and economical whether performed on a large scale or on a relatively small scale. I

It will be further noted that by causing the swage bar with its fullering wings to travel at a relatively high speed in its reciprocating motion and by heating the bit to a'safe degree above the critical temperature prior to the forming operation, that the forming of the cutting surfaces of the bit is greatly facilitated, and that forging machine and over the grinding wheel method of sharpening drill bits.

Other uses and advantages of the improved machine and of my method will be clearly apparent to those skilled in the art. It will be understood that these forms of the invention are shown for purposes of illustration and that, of course, the invention may be modified and embodied in various other forms without departing from the spirit or scope of the claims.

Having thus described my invention, what I claim is: r

1. For sharpening a tooth of a rock drill bit of the type wherein several teeth are radially disposed on the cutting face of a shank body, mechat an angle to the path of travel of the swage bar, said wings having tooth corrugations on the opposed side of the groove to engage and face ward, and meansfor reciprocally moving said swage bar toward and away from said support means. a

2.- For sharpening atooth of a rock drill bit of the type wherein several teeth are radially disposed on the cutting face of a shank body, mech- 10 anism, comprising: means forreceiving a'ncl sup porting the heel of a rock drill bit tooth to be angle to the path of travel of 1 the swage bar, the

opposed sides of the groove between'said wings engaging the sides of a bit tooth and edging the same and pressing the metal of the bit tooth radially outward, and means for reciprocally moving said swage bar toward and away from said support means.

RALPH E. CALHOUN.

V e 3 thesides of the contacted bit tooth, said fullering wings upon contact with a bit tooth edging the same and pressing the metal radially out- 

